The invention refers to a molded body comprising a cell structure and consisting of an elastomeric synthetic plastics material. The invention further refers to a process for producing such a molded body.
The molded body according to the invention shall primarily be used for shoe soles and in particular for shoe soles subjected to severe wear, i.e. for example soles of climber boots, golfer boots, field service boots and worker boots. The molded body according to the invention can, however, also be used for other purposes, above all for purposes in which the molded body is subjected to severe wear, i.e. for example for motor vehicle tires.
It is already known to produce soles and other shoe parts of polyurethane by a polyaddition reaction of liquid reactants resulting in an elastic solid molded body. Up till now the reactants used were polyisocyanates and polyesters or polyethers containing OH-groups. Foaming was effected by adding a liquid of low boiling point or by means of CO.sub.2, thereby obtaining a foam at least partially comprising open cells. Shoe soles produced in such a manner suffer from substantial drawbacks. For example, the danger of fracture under the influence of heat and humidity is very great and the shoe soles become frequently fractured after only few days. Particularly soles consisting of polyether-polyurethane have in addition a low cold elasticity, so that these shoe soles frequently become fractured for this reason on occurrence of low temperatures, and this particularly if the soles were previously contacted with alcaline or acidic media or with humidity under heat. Destruction of the known shoe soles is further enhanced by road dust and dirt entering the open cells and rupturing the thin cell walls during the rolling movement on walking.
The high water resorption capacity of the know shoe soles represents a further drawback being responsible for the uncontrollably changing values of the electric resistance. Such soles can thus not be used for workers boots which shall have insulating properties. Furthermore, the mentioned drawbacks prohibit the use of the known soles of foamed polyurethane at those locations where the soles are subjected to extreme temperature conditions in the presence of humidity.
It is an object of the present invention to provide a molded body comprising a cell structure and having a low apparent density. It is a further object of the invention to provide a molded body which does not absorb water or absorb water in only a small amount and which has an outstanding stability against hydrolysis. The molded body according to the invention shall further be resistant against alcaline and acidic media. It is a further object of the invention to provide a molded body of high inflammability and having outstanding elastic properties on pressure stress. When using a molded body according to the invention as a shoe sole, it is a further object of the invention to give the shoe sole a high sliding resistance even at low temperatures and the desired electrical insulating properties. It is a still further object of the invention to produce a molded body intended to be used as a shoe sole such that shoes provided therewith can without any risk be used as climbers shoes, sporting shoes, workers shoes, safety shoes and field service shoes.